H3C S5820X SERIES High Availability Configuration Manual

Also see for s5800 series: Installation manual Instruction manual Command reference Quick start Troubleshooting guide

Contents

H3C S5820X SERIES High Availability Configuration Manual Manual pdf 128 page image

116Configuring a default route for network hosts facilitates your configuration, but also requires highperformance stability of the device that acts as the gateway. Using more egress gateways is a commonway to improve system reliability, but introduces the problem of routing among the egresses.Virtual Router Redundancy Protocol (VRRP) is designed to address this problem. VRRP adds a group ofrouters that can act as network gateways to a VRRP group, which forms a virtual router. Using the VRRPelection mechanism, routers in the VRRP group elect a master to act as a gateway. Hosts on a LAN onlyneed to configure the virtual router as their default network gateway.VRRP is an error-tolerant protocol. It improves network reliability and simplifies configurations on hosts.On a multicast and broadcast LAN such as Ethernet, VRRP provides highly reliable default links withoutconfiguration changes—such as dynamic routing protocols, route discovery protocols—when a routerfails, and prevents network interruption due to a single link failure.VRRP works in either of the following modes:• Standard protocol mode—Includes two versions VRRPv2 and VRRPv3 based on RFCs. VRRPv2 isbased on IPv4, and VRRPv3 is based on IPv6. The two versions implement the same functions butare applied in different network environments. For more information, see “VRRP standard protocolmode.”• Load balancing mode—Extends the standard protocol mode and realizes load balancing. Formore information, see “VRRP load balancing mode.”VRRP standard protocol modeIntroduction to VRRP groupVRRP combines a group of routers—including a master and multiple backups—on a LAN into a virtualrouter called a VRRP group.A VRRP group has the following features:• A virtual router has a virtual IP address. A host on the LAN only needs to know the IP address of thevirtual router to use the IP address as the next hop of the default route.• Every host on the LAN communicates with external networks through the virtual router.• Routers in the VRRP group elect a master that acts as the gateway according to their priorities. Theother routers function as backups. When the master fails, to ensure that the hosts in the networksegment can uninterruptedly communicate with the external networks, the backups in the VRRPgroup elect a new master to act as the gateway.